JPH0351725B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a hydroxyacrylate polymer in which the resulting polymer can be easily purified. Homopolymers of hydroxyacrylate such as hydroxymethacrylate and copolymers of the acrylate and other radically polymerizable monomers (hereinafter simply referred to as hydroxyacrylate polymers) are:
Conventionally, it has been produced by a so-called homogeneous solution polymerization method in the presence of an organic solvent that can dissolve both the monomer and the polymer obtained by polymerizing it. However, the above method has various difficulties in the purification step for extracting the produced polymer in solid form. That is, when the organic solvent required for polymerization is evaporated, there is a risk that the polymer may be altered by heat, and when the polymer is put into a solvent that serves as a precipitant for the polymer, such as water, together with the organic solvent required for polymerization. A large amount of wastewater is generated, and the cost of processing it becomes enormous. There is also known a precipitation polymerization method in which the resulting polymer is precipitated in the reaction system using a solvent that dissolves the monomer but does not dissolve the polymer obtained by polymerizing the monomer. Regarding the production of the copolymer, a method is known in which, for example, a hydroxyacrylate copolymer containing about 50% by weight of 2-hydroxyethyl acrylate is precipitated using methyl ethyl ketone or cyclohexane as a solvent. However, when methyl ethyl ketone was used, the precipitate became viscous and accumulated on the vessel wall, making it difficult to efficiently remove the polymer. On the other hand, when a hydrocarbon solvent such as cyclohexane is used, a non-adhesive particulate polymer is obtained, but the polymer is completely soluble in highly polar solvents such as methyl cellosolve, dimethyl formamide, dimethyl sulfoxide, and tetrahydrofuran. Therefore, it has been practically impossible to use it in various applications such as adhesives, paints, and printing plate materials. In view of the above-mentioned current state of the prior art, the present invention provides adhesives,
Polymers with sufficient solvent solubility to be used as paints, printing plate materials, etc. are precipitated in the form of non-adhesive particles, that is, precipitated in a heterogeneous system, and easily processed by filtration, centrifugation, etc. This was developed in order to provide a manufacturing method that allows a solid polymer to be extracted by a simple operation, and its gist is that an aliphatic alcohol having 5 to 8 carbon atoms
In the presence of at least one solvent selected from aliphatic alcohol acetate having 5 to 8 carbon atoms and aliphatic ketone having 6 to 8 carbon atoms, the general formula

[Formula] (in which R ₁ and R ₂ each represent H or CH ₃ The present invention relates to a method for producing a hydroxyacrylate polymer, which is characterized by carrying out precipitation polymerization at a temperature of . Suitable examples of the solvent used in the present invention include alcohols such as isoamyl alcohol, hexyl alcohol, and 2-ethylhexyl alcohol, acetate esters such as isopropyl acetate, butyl acetate, and amine acetate, methyl amyl ketone, methyl hexyl ketone, and ethyl Examples include amyl ketone. In the present invention, since the drying temperature in the drying step of purifying the polymer polymerized in the present invention is low, it is preferable that the solvent used in the polymerization has a low boiling point, and it is easy to obtain commercially available products. Particularly suitable solvents include n-butyl acetate, isobutyl acetate, isopropyl acetate, and methyl isobutyl ketone. The monomers represented by the above general formula used in the present invention include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate,
Specific examples of other radically polymerizable monomers when used as a monomer mixture include methyl (meth)acrylate (this means both methyl acrylate and methyl methacrylate; the same applies hereinafter);
Ethyl (meth)acrylate, propyl (meth)
Acrylate, butyl methacrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, (meth)acrylonitrile, dimethylacrylamide, 2-hydroxy Examples include ethyl (methy)acrylamide, vinylpyrrolidone, diacetone acrylamide, dimethyl maleate, and dimethyl fumarate. When the monomer represented by the above general formula or a radically polymerizable monomer mixture containing 30% by weight or more of the monomer is polymerized in the presence of the above organic solvent by a conventional method, the polymer becomes a non-adhesive granular material. Since the solid polymer is precipitated as a substance, a solid polymer can be obtained directly from the polymerization reaction system by means of filtration, centrifugation, drying, etc. When polymerizing a radically polymerizable monomer mixture containing less than 30% by weight of the monomer represented by the above general formula, the obtained polymer will be dissolved in the above solvent, so the conventional method described above should be followed. The polymer must then be purified. The weight ratio of the above monomer/solvent at the start of polymerization is generally 1/2 to 1/10, but if the amount of solvent is too small, the molecular weight of the polymer will become too large, and if the amount of solvent is too large, it is uneconomical. Because there is, preferably 1/4
~1/6. The polymerization initiator that is commonly used as a radical polymerization initiator is widely used, but the lower the polymerization temperature, the smaller the precipitated particles and the easier solid-liquid separation by filtration. It is preferable to use a polyester, and specific examples thereof include benzoyl peroxide and lauroyl peroxide. The present invention is a method for producing a hydroxyacrylate polymer as described above, and according to the present invention, the hydroxyacrylate polymer having good solvent solubility is precipitated as granules without stickiness, so that the reaction can be carried out. It does not stick to the walls of the vessel and can be easily purified by simple filtering, centrifugation, and drying. Examples of the present invention are shown below. The viscosity was measured at 20°C using a 20% by weight methyl cellosolve solution. Examples 1 to 3, Comparative Example 1 A mixture consisting of 45 g of 2-hydroxyethyl methacrylate, 20.5 g of methyl methacrylate, 4.5 g of methacrylic acid, 30 g of acrylonitrile, and 30 g of azoisobutyronitrile was placed in a four-necked separable flask (1). 500 g of the solvent shown in Table 1 was added, and the mixture was stirred at 60°C for 10 hours while passing nitrogen gas. The reaction mixture was cooled to room temperature, the solvent was separated off by suction or decantation and then dried in vacuo. Table 1 shows the state of polymer production at that time.

[Table] Example 4, Comparative Example 2 2-Hydroxypropyl acrylate 15g Benzyl methacrylate 31.5〃 Methyl methacrylic acid 3.5〃 Acrylonitrile 20〃 Azoisobutyronitrile 3g Hydroxyethyl methacrylate 30〃 The mixture of the above composition is shown in Table 2 The polymer obtained by stirring at 60° C. for 3 hours in the same manner as in Examples 1 to 3 in the presence of a solvent was separated and dried in the same manner as in Examples 1 to 3. Table 2 shows the state of polymer production at that time.

[Table] Examples 5 and 6, Comparative Example 3 2-Hydroxyethyl methacrylate 45g Methyl methacrylate 10〃 2-Hydroxy-3-phenoxy acrylate
25〃 Methyl methacrylic acid 5〃 Acrylonitrile 15g Azoisobutyronitrile 3〃 The mixture of the above formulation was stirred at 60°C for 10 hours in the presence of the solvent shown in Table 3 in the same manner as in Examples 1 to 3. The resulting polymer was separated and dried in the same manner as in Examples 1-3. Table 3 shows the state of polymer production at that time.

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Claims (1)

[Scope of Claims] 1. In the presence of at least one solvent selected from aliphatic alcohols having 5 to 8 carbon atoms, acetic esters of aliphatic alcohols having 5 to 8 carbon atoms, and aliphatic ketones having 6 to 8 carbon atoms, A monomer represented by the general formula [formula] (in which R ₁ and R ₂ each represent H or CH ₃ ) or a radically polymerizable monomer mixture containing 30% by weight or more of the monomer, A method for producing a hydroxyacrylate polymer, comprising precipitation polymerization at a temperature of 0.degree. C. or lower. 2. The manufacturing method according to claim 1, wherein the acetate ester of aliphatic alcohol is butyl acetate.